To Alexander Herschel   16.th March 1863

Royal Institution of Great Britain | 16.^th March 1863

My dear Sir

I had replied to your father’s note¹ before I opened yours.² I shall be here early on the day of your lecture³ and we will then have a rehearsal of the experiment you need. I can promise you a first rate Ruhmkorff⁴—gorgeous vacuum tubes, and also a rotating luminous current—I mean rotating under the influence of a magnet. We can do almost anything in the way of optical illustration with an electric lamp, so that on that score your mind may be quite at rest. Seeing the facts you will be able to judge whether they make for or against your theoretic view. If you wish we could fix a day previous to the lecture—say one of the Easter holidays for a preliminary rehearsal. This I think would be the best plan for then if the experiments reveal anything you will be better able make your discourse square with these

Yours very sincerely | John Tyndall

Wellcome, MS. 7777/05